In Outlook, when I open certain messages, there is a fade in the top right corner (see picture). This happens infrequently, but is repeatable for the same message (though I haven't tested across system restarts). Any ideas why it happens? Note that it does not appear for most messages.
For reference this is what the rest of my messages look like. Note that the message with the fade is flagged as a task, but other flagged tasks do not show this behaviour. I do not remember if the previous messages that had this behaviour were flagged.